Making Method For Titania Nanoparticle

ABSTRACT

The present invention relates to a method of manufacturing titania nanoparticles, and specifically to a method of manufacturing titania nanoparticles wherein the particle size is uniform, it is possible to manufacture monodisperse particles without aggregation among particles, a uniform coating can be applied, that is suitable to large-scale production, and that can obtain high-resolution images by maintaining the toner electric charge and electric charge distribution; and the developer included in said titania nanoparticles.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to Korean application number10-2008-0087854, filed on Sep. 5, 2008, which is incorporated herein byreference. This application is also a divisional application of U.S.patent application Ser. No. 12/554,558, filed on Sep. 9, 2009 and titled“Making Method For Titania Nanoparticle” and now U.S. Pat. No. ______.

TECHNICAL FIELD

The present invention relates to a method of manufacturing titaniananoparticles, and more specifically, to a method of manufacturingtitania nanoparticles wherein the particle size is uniform, it ispossible to manufacture monodisperse particles without aggregation amongparticles, a uniform coating can be applied, that is suitable tolarge-scale production, and that can obtain high-resolution images bymaintaining the toner electric charge and electric charge distribution;and the developer included in said titania nanoparticles.

BACKGROUND OF THE INVENTION

The dry developers used in electronic photography may be classified asone-part developers that use the toner itself, in which colorants havebeen dispersed among the terminal resin, and two-part developers whereina carrier is mixed with the toner.

When copying using these developers, in order to establish a suitableprocess, the developer must have excellent fluidity, caking resistance,cohesiveness, electrostatic propensity, and cleaning. Inorganic fineparticles have been added to the toner in order to increase saidfluidity, caking resistance, cohesiveness, and cleaning.

In general, as shown in FIG. 1, external additives typically added tothe toner surface have been inorganic particles such as silica (SiO2)and alumina (Al2O3), fluoride microparticles such as vinylidene fluorideand PTFE (polytetrafluoroethylene), and acryl and stylene-acryl resinmicroparticles manufactured by emulsion polymerization. In FIG. 1, theunits are %.

The inorganic particles of the prior art, such as silica, have adiameter of 7-50 nm and are added in order to provide the toner with thefluidity of a powder. Ordinarily, when an external additive with a lowparticle radius is added to toner, the fluidity is good, but if thesilica particle size is too small, it sometimes occurs that the silicaseparates from the toner surface due to stress applied to the toner,accordingly causing a gradual deterioration in fluidity over time; thesize of the external additive particles has a powerful impact on printquality. In addition, because these inorganic particles exist on the faroutside surface of the toner, they substantially impact theelectrostatic propensity of the toner.

However, hydrophobized silica has strong negative electrostaticpropensity, and hydrophobized alumina has strong positive electrostaticpropensity, thus having a substantial electrostatic impact on the toner.Accordingly, there is an urgent need for a method of manufacturingmonodisperse inorganic particles without aggregation among particles,with nanoscale particles that are also uniform in size and suitable formass production, and that can be used in high-value-addedhigh-definition toners and next-generation color toners that have asmall particle size and require the addition of large quantities ofexternal additives to the toner.

SUMMARY OF THE INVENTION

The present invention, in seeking to resolve the above-describeddeficiencies of the prior art, has as its objective a method ofmanufacturing titania nanoparticles, and specifically to a method ofmanufacturing titania nanoparticles wherein the particle size isuniform, it is possible to manufacture monodisperse particles withoutaggregation among particles, a uniform coating can be applied, that issuitable to large-scale production, and that can obtain high-resolutionimages by maintaining the toner electric charge and electric chargedistribution; the nanoparticles manufactured by said method, and theprovision of said nanoparticles.

In addition, the present invention has the objective of providing adeveloper that enables a uniform coating and the obtaining ofhigh-resolution images by maintaining toner charger and chargedistribution.

In order to attain the above objectives, the present invention providesa method of manufacturing titania nanoparticles comprising: (1) a stagewherein a salt or alkoxide of titania is mixed with a solvent andscanned with microwaves to synthesize a titania precursor; (2) a stagewherein an alkaline catalyst is added to the solvent containing titaniaprecursor obtained in stage (1) above, so as to produce sphericalnanoparticles of titanium hydroxide; (3) a stage wherein crystallinespherical titania particles are made through stages of drying andsintering the titanium hydroxide obtained in step (2) above; and (4) astep wherein the nanoparticles obtained in step (3) above arehydrophobized.

In addition, the present invention provides monodisperse sphericaltitania nanoparticles manufactured by said method.

Further, the present invention provides a developer that includes saidspherical titania nanoparticles.

According to the method of manufacturing titania nanoparticles of thepresent invention, the size of particles is uniform, the manufacture ofmonodisperse particles without aggregation between particles is madepossible, a uniform coating is made possible, and images of highresolution suitable for mass production can be obtained by maintainingthe charge and charge distribution of the toner; when the toner externaladditive for developing obtained from said titania nanoparticles isused, a uniform coating is possible, and high-resolution images can beobtained by maintaining the charge and charge distribution of the toner.

BRIEF EXPLANATION OF DRAWINGS

FIG. 1 shows a schematic diagram of toner that contains an externaladditive

FIG. 2 is a schematic diagram of the titania nanoparticle manufacturingmethod of the present invention, including a microwave scanning device

FIGS. 3 through 6 are scanning electron microscopy (SEM) photographs oftitania nanoparticle manufactured according to the respective practicalexamples of the present invention.

FIGS. 7 through 10 are photographs of the contact angle with respect towater of the titania nanoparticles manufactured according to therespective practical examples of the present invention.

DETAILS OF THE IMPLEMENTATION OF THE INVENTION

Hereinbelow, the present invention is described in detail.

The toner described herein below in this specification (“toner”)includes both color toner and black/white toner. In addition,“spherical” refers not solely to a perfect sphere, but includesspheroids with a sphericity of 0.6-1. Sphericity (in the case of asphere) refers to the ratio of the surface of area of a sphere havingthe same volume as the actual particle to the surface area of the actualparticle.

The method of manufacturing titania nanoparticles of the presentinvention enables the manufacturing of particles of a uniform size andis appropriate for mass production according to studies of the synthesisprocess technology for spherical titania nanoparticles, and can resolvethe problems in aggregation due to positive or negative charge occurringwhen using an external toner additive such as the silica or alumina ofthe prior art, through coating the surface of the monodisperse sphericalparticle with a hydrophobic substance.

The method of manufacturing titania nanoparticles of the presentinvention comprises: (1) a stage wherein a salt or alkoxide of titaniais mixed with a solvent and scanned with microwaves to synthesize atitania precursor; (2) a stage wherein an alkaline catalyst is added tothe solvent containing titania precursor obtained in stage (1) above, soas to produce spherical nanoparticles of titanium hydroxide; (3) a stagewherein crystalline spherical titania particles are made through stagesof drying and sintering the titanium hydroxide obtained in step (2)above; and (4) a stage wherein the nanoparticles obtained in step (3)above are hydrophobized.

The individual steps of the method of manufacturing titaniananoparticles of the present invention can be described in detail asfollows.

The present step involves the making of a spherical titania precursor byfirst mixing titanium salt or titanium alkoxide with solvent and thenscanning with microwaves; the microwaves used have a wavelength of300-3000 MHz; the solvent is instantly heated by the microwave scanning,and the titania precursor is formed.

It is preferable in this step (1) that the solvent be passed through areaction tube that is scanned by the microwaves, as depicted in FIG. 2;by way of a specific example, it is possible to adjust the reactionoutlet temperature to 70-80° C. by proceeding at a solvent fluidvelocity of 300-1500 cc/min in the reaction tube furnished by amicrowave scanning deice with a maximum output of 5 kW, having anisolator and a magnetron generating 2450 MHz, and setting the reactionspeed pass-through time 10-60 sec.

For said titania salt, for example titanium oxychloride, titaniumchloride, titanium nitrate, or titanium sulfate may be used; for saidtitanium alkoxide, a C1-C12 titanium alkoxide may be used; by way of aspecific example, titanium ethoxide, titanium isopropoxide, or titaniumbutoxide may be used.

Said solvent is not limited to any solvent that can dissolve titaniumsalt or titanium alkoxide; by way of specific example, water, alcohol oran aqueous solution of alcohol may be used. For the alcohol, it ispreferable that a C1-C5 alcohol be used; specific examples includemethyl alcohol, ethyl alcohol, propyl alcohol, isopropyl alcohol, andbutyl alcohol, either singly or in mixture; it is most preferable thatthe solvent be an aqueous solution of alcohol containing 30-95 vol %alcohol.

In addition, the concentration of said titania salt or titania alkoxidein the solvent should be 0.1-1 M/liter; a dispersant may be used toprevent aggregation, and said dispersant may be such as HPC, PVA, orPVP; of these, HPC allows the most monodisperse particles to beobtained; the quantity of dispersant used should preferably be 0.1-2 gper liter of the total mixture.

In Step (2) of the present invention, an alkaline catalyst is added tothe solution containing the titania precursor obtained in step (1)above, to produce titanium hydroxide. Here it is preferable that the pHof the solution be adjusted to the 5-10 range by the addition of saidalkali.

Said alkaline catalyst may suitably be a compound containing an amine orhydroxy group, or an aqueous solution thereof; specific examples of thisinclude ammonia, sodium hydroxide, alkyl amines, and mixtures thereof.

In step (3) of the present invention, the titania hydroxide obtained instep (2) above is dried and sintered; it is preferable that this dryingbe performed for 4 to 12 hours at 100-130° C., after preparatory dryingfor 1 to 3 hours at 50-70° C. In addition, the sintering step involvesimparting a crystalline character; it is preferable that sintering beperformed for 1 to 4 hours at 600-800° C. so as to acquire a rutileshape.

Next, in step (4) of the present invention, the surface of the titaniananoparticles obtained in step (3) above is hydrophobized so as finallyto produce titania nanoparticles with a hydrophobized surface.

Said hydrophobization may be performed using an ordinary silane couplingagent or titanium coupling agent; specific examples of a silane coupleagent include the hydrophobization agents hexamethyldisilazane (HMDS),methyltrimethoxysilane (MTMS), dimethyldiethoxysilane (DMDES), andtrimethylethoxysilane (TMES); specific examples of a titanium couplingagent include the hydrophobization agents isopropyl triisostearoyltitanate (KR-TTS), isopropyl dimethaacryl isostearoyl titanate (KR-7),isopropyl tri(dodecyl)benzenesulfonyl titanate(KR-9S), isopropyltri(dioctyl)pyrophosphato titanate (KR-38S), di(cumyl)phenyl oxoethylenetitanate (KR-134S), di(dioctyl)pyrophosphate oxoethylene titanate(KR-138S), neopentyl(diallyl)oxy, and tri(dioctyl)pyro-phosphatotitanate (LICA-38).

Said hydrophobization agent may be used in quantities of 1 to 20 weightparts per 100 weight parts of titania nanoparticles (relative to thesolid component).

The titania nanoparticles manufactured according to the presentinvention described above have a monodisperse, spherical form withnearly identical size; the surfaces of these monodisperse sphericalparticles is coated with a hydrophobic substance, thereby enablingeffective use as a external toner additive.

The size of titania nanoparticles of the present invention, thusmanufactured, can be adjusted at will; when used as an external toneradditive, the size should be from 30 to 200 nm; as needed, the spheresmay have a median diameter of 30 nm, 50 nm, 100 nm, 150 nm, or 200 nm.

In addition, the titania nanoparticles of the present invention show acontact angle of 100° or greater with respect to water. (In the case ofthe contact angle with water, the measured limit value was 170°, but intheory it could be up to 180°.) If said contact angle with water is lessthan 100°, hydrophobicity will suffer and when used as an external toneradditive, the print quality of the toner may suffer due to either theadsorption of airborne moisture or the formation of aggregates.

In addition, it is preferable that the specific surface area of thetitania nanoparticles be between 20 and 100 m²/g. If said specificsurface area is less than 20 m²/g, the aggregation of particles may besevere; because this makes it difficult for the final coating of thetoner with external additive to be uniform, it may cause a problematicdeterioration in toner print quality; if it exceeds 100 m²/g, thisindicates that the initial particles will be very small, which alsomakes the hydrophobic coating of individual particles difficult; thismay cause a problematic failure of some areas to print due to the tonersurface being completely surrounded even at low quantities.

The titania nanoparticles of the present invention manufactured asabove-described may be used as external toner additives, andspecifically as external toner additives for electrostatic imagedevelopment. Said external toner additives may be used separately, oralso as two or more types together.

When said titania nanoparticles are used as an external toner additive,the ratio of admixture should preferably be from 0.01 to 20 weight partswith respect to 100 weight parts of toner particles; it is even morepreferable that 0.1 to 5 weight parts be used. If the admixture ratio iswithin said range, sufficient adhesion to the toner particles willoccur, and not only will good fluidity be obtained, but there will alsobe a positive improvement in the electrostatic propensity of the tonerparticles.

Said titania nanoparticles can simply adhere mechanically to the tonerparticle surface, or may also be fixed gradually to the surface. Inaddition, the entire surface of the toner particle may be covered, or aportion may be covered.

Toner for electrostatic image development using titania nanoparticles asan external toner additive as above-described may be used as asingle-component developer, but it is also possible to blend this with acarrier and use as a 2-component developer. When used as a 2-componentdeveloper, the external toner additive should not be added to the tonerparticles in advance, but only when the carrier is mixed with the tonerparticles to carry out the surface coating of the toner particles.

This carrier can be any commonly-known carrier such as iron, and can bemixed according to the mixing ratios that are commonly known.

Herein below, in order to assist in the understanding of the presentinvention, preferred embodiments are presented; however, theseembodiments merely exemplify the present invention and the scope of thepresent invention is not limited by the embodiments below.

PRACTICAL EXAMPLES Practical Example 1 Manufacture of Spherical TitaniaNanoparticles of 30 nm Diameter

A microwave scanning device (Japan Radio Corporation, JRC: microwavegeneration device (NJA)) was furnished as shown in FIG. 1 and synthesiswas carried out under the conditions of Table 1 below; as a result,spherical titania precursors with an average diameter of 30 nm could beobtained, and after filtering and drying these, heat treatment wasperformed to yield a powder of titania nanoparticles having a size of 30nm.

The specific surface area of said powder was measured to be 58 m2/g.Said yielded titania nanoparticles were added to dimethyldiethoxysilane(DMDES) at 16.57 weight parts per 100 weight parts, and refluxing andhydrophobization was performed thereon to obtain titania nanoparticles.The contact angle of the surface-treated titania nanoparticles wasconfirmed by measurement to be at least 150°, as shown in FIG. 7.

Practical Example 2 Manufacture of Spherical Titania Nanoparticles of 50nm Diameter

The microwave scanning device (please indicate manufacturer and productname) used in Practical Example 1 above was employed and synthesis wascarried out under the conditions of Table 1 below; as a result,spherical titania precursors with an average diameter of 50 nm could beobtained, and after filtering and drying these, heat treatment wasperformed to yield a powder of titania nanoparticles having a size of 50nm, as shown in FIG. 4. The specific surface area of said powder wasmeasured to be 42 m2/g. Said yielded titania nanoparticles were added todimethyldiethoxysilane (DMDES) at 12 weight parts per 100 weight parts,and refluxing and hydrophobization was performed thereon to obtaintitania nanoparticles. The contact angle of the surface-treated titaniananoparticles was confirmed by measurement to be at least 150°, as shownin FIG. 8.

Practical Example 3 Manufacture of Spherical Titania Nanoparticles of100 nm Diameter

The microwave scanning device (please indicate manufacturer and productname) used in Practical Example 1 above was employed and synthesis wascarried out under the conditions of Table 1 below; as a result,spherical titania precursors with an average diameter of 100 nm could beobtained, and after filtering and drying these, heat treatment wasperformed to yield a powder of titania nanoparticles having a size of100 nm, as shown in FIG. 5. The specific surface area of said powder wasmeasured to be 25 m2/g. Said yielded titania nanoparticles were added todimethyldiethoxysilane (DMDES) at 7.14 weight parts per 100 weightparts, and refluxing and hydrophobization was performed thereon toobtain titania nanoparticles. The contact angle of the surface-treatedtitania nanoparticles was confirmed by measurement to be at least 150°,as shown in FIG. 9.

Practical Example 4 Manufacture of Spherical Titania Nanoparticles of200 nm Diameter

The microwave scanning device (please indicate manufacturer and productname) used in Practical Example 1 above was employed and synthesis wascarried out under the conditions of Table 1 below; as a result,spherical titania precursors with an average diameter of 200 nm could beobtained, and after filtering and drying these, heat treatment wasperformed to yield a powder of titania nanoparticles having a size of200 nm, as shown in FIG. 5. The specific surface area of said powder wasmeasured to be 17 m2/g. Said yielded titania nanoparticles were added todimethyldiethoxysilane (DMDES) at 4.86 weight parts per 100 weightparts, and refluxing and hydrophobization was performed thereon toobtain titania nanoparticles. The contact angle of the surface-treatedtitania nanoparticles was confirmed by measurement to be at least 150°C., as shown in FIG. 10.

TABLE 1 Operation Example 1 Example 2 Example 3 Example 4 TiOCl2concentration 0.02M 0.04M 0.06M 0.1M IPA/H2O (by volume) 5 5 5 5Reaction outlet 76 77 78 73 temperature (C.) Flow Rate (cc/min) 1020 910800 750 Res. Time (sec) 12.7 14.1 16.2 17.6 pH (NH4OH 1N 7.57 8.87 8.438.20 solution) Output Sample Average diameter (nm) ≈30 . . . ≈50 . . .≈100 . . . ≈200 . . .

Practical Examples 5 through 8 Manufacture of Toner Mixed With ExternalAdditive (Including a Developer Component).

After fusing 4 weight parts of colorant (product name: Carmine 6BC,Smika Color Mfr.) to 96 weight parts of polyester resin with a softeningpoint of 100° C. and a glass transition temperature of 60° C., whilekneading and crushing, it was separated to yield toner with an averageparticle diameter of 7 μm. Toner mixed with external additives wasmanufactured (Practical Examples 5-8) by mixing 0.3 g each of thetitania nanoparticles produced in Practical Examples 1 through 4 aboveto 10 g of this toner.

In order to verify the performance of the developer of the presentinvention, the developer produced in Practical Examples 5 through 8above was used and measured with respect to the quantity of toner used,by the method below; the results thereof are shown in Table 2.

Measurement was performed by

a) a step wherein the weight of the CRU (toner cartridge) was measuredbefore performing the experiment;

(b) a step wherein 5000 prints were made on writing/A4 sized paper;

(c) a step wherein after the completion of 5000 prints, the weight ofthe CRU was measured, and

(d) a step wherein the consumption of toner per 5000 prints wasobtained, and next the

amount of toner consumed in print 1 sheet was obtained. By way of acomparison example, a developer manufactured in the same fashion asPractical Example 5, except that none of the above-described titaniananoparticles of the present invention were used, was employed(Comparison Example 1).

TABLE 2 1-component developer Example 5 Example 6 Example 7 Example 8Example 1 Toner usage 17.7 18.3 16.9 19.6 23.8 (mg/pg @78/80)

When the developer of Examples 5-8 of the present invention was used, aclear image of high quality was obtained in the prints, and inparticular, as is apparent in Table 2, a clear reduction in tonerconsumption could be observed.

1. A composition comprising: hydrophobized titania nanoparticlesproduced from dried and sintered titanium hydroxide, the titaniumhydroxide being produced by mixing a salt or alkoxide of titania with asolvent and scanning with microwaves to synthesize a titania precursor,then adding an alkaline catalyst to the solvent so as to producespherical nanoparticles of titanium hydroxide.
 2. The composition ofclaim 1, wherein the titania salt or titania alkoxide comprises one ormore compounds selected from the group consisting of titaniumoxychloride, titanium chloride, titanium nitrate, titanium sulfate, andC1-C12 titanium alkoxides.
 3. The composition of claim 1, wherein thealkaline catalyst comprises at least one of an amine, a hydroxy group,or an aqueous solution of same.
 4. The composition of claim 1, whereinthe pH of the mixture is maintained between 5 and 10 after the additionof the alkaline catalyst.
 5. The composition of claim 1, wherein thespherical nanoparticles are dried over a period of about 4 to about 12hours at a temperature in the range of from about 100 to about 130° C.after preparatory drying at a temperature in the range of from about 50to about 70° C. for a period in the range of from about 1 to about 3hours.
 6. The composition of claim 1, wherein the sphericalnanoparticles are sintered for a period of from about 1 to about 4 hoursat a temperature in the range of from about 600 to about 800° C.
 7. Thecomposition of claim 1, further comprising one or more hydrophobizationagents chosen from among the group comprising hexamethyldisilazane(HMDS), methyltrimethoxysilane (MTMS), dimethyldiethoxysilane (DMDES),and trimethylethoxysilane (TMES), isopropyl triisostearoyl titanate(KR-TTS), isopropyl dimethaacryl isostearoyl titanate (KR-7), isopropyltri(dodecyl)benzenesulfonyl titanate(KR-9S), isopropyltri(dioctyl)pyrophosphato titanate (KR-38S), di(cumyl)phenyl oxoethylenetitanate (KR-134S), di(dioctyl)pyrophosphate oxoethylene titanate(KR-138S), neopentyl(diallyl)oxy, and tri(dioctyl)pyro-phosphatotitanate (LICA-38).
 8. The composition of claim 7, wherein thehydrophobization agent is used in a range of from about 1 to about 20weight parts with respect to 100 weight parts of solid crystallinetitania nanoparticles.
 9. The composition of claim 1, wherein theaverage diameter of said titania nanoparticles is in a range of fromabout 30 to about 200 nm, and the specific surface area is in a range offrom about 20 to about 100 m²/g.
 11. The composition of claim 9, whereinthe titania nanoparticles have a contact angle with respect to water ina range of from about 100 to about 170 ° C.
 12. The composition of claim1, further comprising a carrier.